U.S. patent number 10,646,315 [Application Number 13/133,129] was granted by the patent office on 2020-05-12 for dental curing light having unibody design that acts as a heat sink.
This patent grant is currently assigned to ULTRADENT PRODUCTS, INC.. The grantee listed for this patent is Dee Jessop, Neil Jessop, Jared Sheetz. Invention is credited to Dee Jessop, Neil Jessop, Jared Sheetz.
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United States Patent |
10,646,315 |
Jessop , et al. |
May 12, 2020 |
Dental curing light having unibody design that acts as a heat
sink
Abstract
A dental curing light includes a device body that efficiently
conducts heat away from the light emitting diode portion of the
curing light. The device body includes a proximal gripping end and
a distal head end. The device body is formed from a thermally
conductive body material. Excellent heat conduction away from the
LED dies is achieved using a thermally conductive layer disposed
over the device body. The thermally conductive layer serves as a
conduit to quickly conduct heat away from the LED dies for
dissipation within the material of the device body In this manner,
the material of the device body serves as a highly efficient heat
dissipater. The surface area coupling the thermally conductive
layer to the device body is sufficiently large that a majority (e
g, substantially all) of heat being conducted by the thermally
conductive layer is transferred to the device body during operation
of the device.
Inventors: |
Jessop; Dee (Salt Lake City,
UT), Sheetz; Jared (Eagle Mountain, UT), Jessop; Neil
(Sandy, UT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Jessop; Dee
Sheetz; Jared
Jessop; Neil |
Salt Lake City
Eagle Mountain
Sandy |
UT
UT
UT |
US
US
US |
|
|
Assignee: |
ULTRADENT PRODUCTS, INC. (South
Jordan, UT)
|
Family
ID: |
42310196 |
Appl.
No.: |
13/133,129 |
Filed: |
December 29, 2009 |
PCT
Filed: |
December 29, 2009 |
PCT No.: |
PCT/US2009/069738 |
371(c)(1),(2),(4) Date: |
August 24, 2011 |
PCT
Pub. No.: |
WO2010/078368 |
PCT
Pub. Date: |
July 08, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20110300505 A1 |
Dec 8, 2011 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61141482 |
Dec 30, 2008 |
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61174873 |
May 1, 2009 |
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61174843 |
May 1, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61C
19/003 (20130101); A61C 19/004 (20130101) |
Current International
Class: |
A61C
13/15 (20060101) |
Field of
Search: |
;433/29 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1276917 |
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0678282 |
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EP |
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1138276 |
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2417876 |
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2000232284 |
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JP |
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Nov 2004 |
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JP |
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WO9922667 |
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May 1999 |
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WO |
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WO2001064129 |
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Sep 2001 |
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WO |
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WO2004011848 |
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Jul 2003 |
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WO |
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WO2005081947 |
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Sep 2005 |
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WO |
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WO2006107122 |
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Oct 2006 |
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WO |
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Other References
Sherman, Lilli Manolis; "Plastics that Conduct Heat", Jun. 2001,
Plastics Technology. cited by examiner .
U.S. Appl. No. 61/141,482, filed Dec. 30, 2008, Jessop, et al.
cited by applicant .
Barton, Daniel L. et al. "Phototonic Chrystals Improve LED
Efficiency". http://spie.org/x8796.xml. Apr. 17, 2006. cited by
applicant .
Japanese Office Action cited in Japanese Application No.
20150227914 dated Aug. 1, 2017. cited by applicant.
|
Primary Examiner: Moran; Edward
Attorney, Agent or Firm: Workman Nydegger
Claims
What is claimed is:
1. A dental curing light device, comprising: an elongated unitary,
one-piece body formed from a continuous seamless piece of thermally
conductive material extending between a proximal end and a distal
end along a longitudinal axis, the continuous seamless piece
comprising: a head portion extending to the distal end and having a
recess in a first side of the continuous seamless piece; a neck
tapering outward from the head portion; and a handle portion
extending to the proximal end of the continuous seamless piece, the
handle portion having a cavity formed along the longitudinal axis
and an opening through a second side of the continuous seamless
piece opposite the first side; an LED assembly disposed at least
partially in the recess and thermally coupled to the head portion,
the LED assembly including one or more LED dies and a thermally
conductive LED assembly substrate; a thermally conductive layer
that thermally couples the LED assembly to the head portion; an
electronics assembly disposed at least partially within the cavity
in the handle portion of the continuous seamless piece; and a power
cord extending from, or an electrical plug or connection disposed
at, the proximal end of the continuous seamless piece.
2. The dental curing light device of claim 1, wherein the thermally
conductive layer is in direct contact with the head portion of the
continuous seamless piece of thermally conductive material.
3. The dental curing light device of claim 1, wherein a surface
area coupling the thermally conductive layer with the head portion
is as large or larger than a surface area coupling the thermally
conductive layer with the LED assembly substrate.
4. The dental curing light device of claim 1, wherein a surface
area coupling the thermally conductive layer with the head portion
is at least 10% larger than a surface area coupling the thermally
conductive layer with the LED assembly substrate.
5. The dental curing light device of claim 1, the electronics
assembly comprising electrical circuitry configured to drive the
one or more LED dies to an output light intensity of at least 2000
mW/cm.sup.2.
6. The dental curing light device of claim 1, the electronics
assembly comprising electrical circuitry configured to drive the
one or more LED dies to an output light intensity of at least 3000
mW/cm.sup.2.
7. The dental curing light device of claim 1, the electronics
assembly comprising electrical circuitry configured to drive the
one or more LED dies with a maximum input power that is less than
70% of a rated maximum power of the one or more LED dies while
achieving a luminescence of at least 800 mW/cm.sup.2.
8. The dental curing light device of claim 1, wherein the thermally
conductive layer comprises a piece separate from the continuous
seamless piece having a thickness in a range of 100 microns to 1.5
mm.
9. The dental curing light device of claim 1, wherein the thermally
conductive layer comprises a material applied to the head portion
of the continuous seamless piece and having a thickness in a range
of 0.05 micron to 50 microns.
10. The dental curing light device of claim 1, wherein the
thermally conductive layer has a thermal conductivity greater 150
W/m-K.
11. The dental curing light device of claim 1, wherein the
thermally conductive layer has a thermal conductivity greater 300
W/m-K.
12. The dental curing light device of claim 1, wherein the
thermally conductive layer has a higher thermal conductivity than
the thermally conductive material of the continuous seamless
piece.
13. The dental curing light device of claim 1, wherein the
thermally conductive layer is selected from the group consisting of
aluminum nitride, beryllium oxide, diamond, silicon carbide, boron
nitride, and combinations thereof.
14. The dental curing light device of claim 1, wherein the
thermally conductive layer is thermally coupled to the LED assembly
substrate by a thermally conductive adhesive.
15. The dental curing light device of claim 1, wherein the
thermally conductive material of the continuous seamless piece
comprises a metal selected from the group consisting of aluminum,
copper, magnesium, and alloys thereof.
16. The dental curing light device of claim 15, further comprising
an anodized material on an exterior surface of the continuous
seamless piece that provides scratch resistance to the metal.
17. The dental curing light device of claim 1, wherein the
thermally conductive material of the continuous seamless piece
comprises a thermally conductive ceramic fiber selected from the
group consisting of carbon fiber, boron fiber, boron nitride fiber,
and combinations thereof.
18. The dental curing light device of claim 1, wherein the
continuous seamless piece is substantially straight with the head
portion having a thickness between 1 mm and 15 mm and the handle
portion having a thickness between 10 mm and 40 mm.
19. The dental curing light device of claim 1, wherein the one or
more LED dies includes a first LED die that emits in the blue
region of the light spectrum and a second LED die that emits in the
ultraviolet (UV) region of the light spectrum.
20. The dental curing light device of claim 1, further comprising a
lens or a photonic crystal at the head portion of the continuous
seamless piece, the lens or photonic crystal being configured to
focus light emitted from the one or more LED dies.
21. The dental curing light device of claim 20, further comprising
an anti-reflective coating on at least a portion of the lens.
22. The dental curing light device of claim 20, further comprising
a reflective collar having a reflective coating on an interior
surface thereof, the reflective collar being positioned between the
one or more LED dies and the lens or photonic crystal, the
reflective collar defining an opening configured to reflect and
channel light from the one or more LED dies into the lens or
photonic crystal.
23. The dental curing light device of claim 22, wherein the
reflective coating comprises a noble metal.
24. The dental curing light device of claim 1, further comprising a
thermally conductive removable member that is removably received
within the recess in the head portion of the continuous seamless
piece, wherein the thermally conductive layer and the LED assembly
are attached to the thermally conductive removable member.
25. The dental curing light device of claim 24, wherein the recess
in the head portion includes a threaded opening formed through the
head portion, wherein the thermally conductive removable member
comprises a thermally conductive cup thermally and threadably
coupled to the head portion at the threaded opening.
26. The dental curing light device of claim 1, wherein the
thermally conductive layer includes traces in electrical contact
with one or more contacts of the LED assembly.
27. The dental curing light device of claim 1, wherein the
thermally conductive layer comprises a printed circuit board.
28. The dental curing light device of claim 27, wherein the
thermally conductive layer comprises at least one of a ceramic
printed circuit board or a metalized printed circuit board.
29. The dental curing light device of claim 1, wherein the
thermally conductive layer includes a thermally conductive grease
or gel having one or more thermally conductive filler
materials.
30. The dental curing light device of claim 1, wherein the
thermally conductive layer includes a thermally conductive grease
selected from the group consisting of silicon grease, polymer
grease, metalized grease, nano-particle grease, and combinations
thereof.
31. The dental curing light device of claim 1, wherein the
thermally conductive layer includes a deformable pad.
32. The dental curing light device of claim 1, further comprising a
protective coating covering at least a portion of the continuous
seamless piece of thermally conductive material between the head
portion and the handle portion.
33. The dental curing light device of claim 32, wherein the
protective coating comprises at least one of fluoropolymer or
parylene.
34. The dental curing light device of claim 1, further comprising a
scratch resistant material on an exterior surface of the continuous
seamless piece.
35. The dental curing light device of claim 34, wherein the scratch
resistant material is selected from aluminum oxide
(Al.sub.2O.sub.3), aluminum nitride (AlN), and combinations
thereof.
36. The dental curing light device of claim 1, wherein the
electronics assembly is configured to ramp the light intensity over
a period of time and wherein the electronics assembly provides for
selection of longer and shorter periods of time for the ramp
period.
37. The dental curing light device of claim 36, wherein a first
ramp time is in a range from 3 to 7 seconds, and a second ramp time
is in a range from 8 to 12 seconds.
38. The dental curing light device of claim 1, wherein the opening
through the second side of the continuous seamless piece is an
elongated opening extending along a majority of the length of the
handle portion of the continuous seamless piece, the electronics
assembly including a control panel extending and/or being
accessible through the elongated opening.
39. The dental curing light device of claim 1, wherein the
continuous seamless piece is formed by machining a single piece of
the thermally conductive material.
40. The dental curing light device of claim 1, further comprising a
power cord hole at the proximal end of the continuous seamless
piece through which the power cord passes, and wherein the power
cord is coupled to the electronics assembly.
41. A dental curing light device, comprising: an elongated unitary,
one-piece body formed from a continuous seamless piece of thermally
conductive material extending along a longitudinal axis between a
proximal end and a closed distal end, the continuous seamless piece
comprising: a head portion extending to the closed distal end and
having a threaded opening formed through a first side of the
continuous seamless piece; a neck tapering outward from the head
portion; and a handle portion extending to the proximal end of the
continuous seamless piece, the handle portion including a cavity
formed along the longitudinal axis and opening through a second
side of the continuous seamless piece opposite the first side; an
LED assembly disposed within a thermally conductive cup thermally
and threadably coupled to the head portion at the threaded opening,
the LED assembly including one or more LED dies and a thermally
conductive LED assembly substrate; a thermally conductive layer
that thermally couples the LED assembly to the thermally conductive
cup; an electronics assembly at least partially disposed within the
cavity in the handle portion of the continuous seamless piece; and
a power cord extending from, or an electrical plug or connection
disposed at, the proximal end of the continuous seamless piece.
42. A dental curing light device, comprising: an elongated unitary,
one-piece body formed from a continuous seamless piece of thermally
conductive material extending along a longitudinal axis between a
proximal end and a distal end, the continuous seamless piece
comprising: a light emitting head portion extending to the distal
end and having a cavity in a first side of the continuous seamless
piece; a neck tapering outward from the head portion; and a handle
portion extending to the proximal end of the continuous seamless
piece, the handle portion including a cavity formed along the
longitudinal axis and comprising an elongated opening through the
handle portion on the second side of the continuous seamless piece
and extending along a majority of the length of the handle portion;
an LED assembly thermally coupled to the head portion, the LED
assembly including one or more LED dies and a thermally conductive
LED assembly substrate; a thermally conductive layer that thermally
couples the LED assembly to the head portion; an electronics
assembly at least partially disposed within the internal cavity in
the handle portion of the continuous seamless piece, the
electronics assembly including a control panel extending and/or
being accessible through the elongated opening; and a power cord
extending from, or an electrical plug or connection disposed at,
the proximal end of the continuous seamless piece.
43. The dental curing light device of claim 1, wherein the
continuous seamless piece provides an entire length of thermally
conductive material between the distal end and the proximal
end.
44. The dental curing light device of claim 1, wherein the dental
curing light is cordless and comprises the electrical plug or
connection at the proximal end of the continuous seamless
piece.
45. The dental curing light device of claim 44, further comprising
a rechargeable battery within the cavity.
46. The dental curing light device of claim 41, further comprising
a power cord hole at the proximal end of the continuous seamless
piece configured to receive the power cord.
47. The dental curing light device of claim 46, wherein the power
cord is coupled to the electronics assembly.
48. The dental curing light device of claim 46, further comprising
a protective sleeve attached to the proximal end of the continuous
seamless piece and cooperating with the power cord to enclose the
power cord hole.
49. A dental curing light device, comprising: an elongated unitary,
one-piece body formed from a continuous seamless piece of thermally
conductive material extending along a longitudinal axis between a
proximal end and a distal end, the continuous seamless piece
comprising: a light emitting head portion extending to the distal
end and having a cavity in a first side of the continuous seamless
piece; a neck tapering outward from the head portion; and a handle
portion extending to the proximal end of the continuous seamless
piece, the handle portion including an internal cavity formed along
the longitudinal axis; an LED assembly thermally coupled to the
head portion, the LED assembly including one or more LED dies and a
thermally conductive LED assembly substrate; a thermally conductive
layer that thermally couples the LED assembly to the head portion;
an electronics assembly at least partially disposed within the
internal cavity of the handle portion of the continuous seamless
piece; a rechargeable battery disposed within the internal cavity
of the handle portion of the continuous seamless piece of thermally
conductive material; and an electrical plug or connection disposed
at the proximal end of the continuous seamless piece for recharging
the rechargeable battery.
50. The dental curing light device of claim 49, wherein the
continuous seamless piece extends along an entire length between
the distal end and the electrical plug or connection disposed at
the proximal end.
51. The dental curing light device of claim 49, wherein the
continuous seamless piece provides an entire length of the dental
curing light device between the distal end and the electrical plug
or connection.
52. A dental curing light device, comprising: an elongated unitary,
one-piece body formed from a continuous seamless piece of thermally
conductive material extending along a longitudinal axis between a
proximal end and a distal end, the continuous seamless piece
comprising: a light emitting head portion extending to the distal
end and having a cavity in a first side of the continuous seamless
piece; a neck tapering outward from the head portion; a handle
portion extending to the proximal end of the continuous seamless
piece, the handle portion including a cavity formed along the
longitudinal axis and opening through a second side of the
continuous seamless piece opposite the first side; and a power cord
hole at the proximal end of the continuous seamless piece
configured to receive a power cord; an LED assembly thermally
coupled to the head portion, the LED assembly including one or more
LED dies and a thermally conductive LED assembly substrate; a
thermally conductive layer that thermally couples the LED assembly
to the head portion; an electronics assembly disposed within the
cavity of the handle portion; a protective sleeve abutting and
extending proximally from the proximal end of the continuous
seamless piece; and a power cord extending from the proximal end of
the continuous seamless piece and received through the protective
sleeve and the power cord hole.
53. The dental curing light device of claim 52, wherein the power
cord is coupled to the electronics assembly.
54. The dental curing light device of claim 52, wherein the
protective sleeve is formed from an electrically insulating
material.
Description
BACKGROUND
1. The Field of the Invention
The present invention generally relates to the field of light
curing devices. More particularly, the invention relates to light
curing devices including one or more light emitting diodes (e.g.,
LEDs) for providing light curing wavelengths configured to cure
polymerizable compositions.
2. The Relevant Technology
In the field of dentistry, dental cavities or preparations are
often filled and/or sealed with photosensitive polymerizable
compositions that are cured by exposure to radiant energy, such as
visible light. These compositions, commonly referred to as
light-curable compositions, are placed within dental cavity
preparations or onto dental surfaces where they are subsequently
irradiated by light. The radiated light causes photosensitive
components within the compositions to initiate polymerization of
polymerizable components, thereby hardening the light-curable
composition within the dental cavity preparation or other dental
surface.
Light-curing devices are typically configured with an activating
light source, such as a quartz-tungsten-halogen (QTH) bulb or light
emitting diodes (LEDs). QTH bulbs generate a broad spectrum of
light that can be used to cure a broad range of polymerizable
compositions. QTH bulbs generate substantial waste heat and require
bulky surrounding structure to draw waste heat away from the bulb
and to dissipate the waste heat.
Use of LED light sources has been a significant improvement in
dental curing devices. LEDs are smaller than QTH bulbs and
generally radiate light at a narrow range surrounding a specific
peak wavelength. They often require significantly less input power
to generate a desired output of radiation. In addition, LED light
sources provide a longer life (e.g., tens of thousands of hours or
more) than QTH bulbs. However, thermal management (e.g.,
dissipating heat) is still an issue with devices which include LED
light sources.
While prior LED curing light devices may produce less waste heat
than bulb curing devices, LED curing devices still tend to produce
waste heat that significantly raises the temperature of the LED and
immediately surrounding structures during illumination. This
increase in temperature may reduce the useful life of the LED. LEDs
can burn out due to overheating within a matter of minutes,
requiring replacement of the LED light source if the heat is not
dissipated.
SUMMARY
The present invention is directed to curing light devices that
efficiently dissipate heat away from a light emitting diode (LED)
during use. The dental curing light devices include a device body
having a proximal gripping end (i.e., handle portion) connected to
a distal head portion by a neck portion. The device body is
advantageously formed from one or more thermally conductive body
materials (e.g., thermally conductive metal, polymer, ceramic,
and/or thermally conductive ceramic fibers or nanomaterials). In
one embodiment, the device body is one continuous piece with no
joints (i.e., a "unibody" construction). All or a portion of the
device body can be made from the thermally conductive body material
so long as the device body has sufficient thermal conductivity to
dissipate the desired heat generated by the LED during use (i.e.,
with the device set to a maximum user selectable light output). In
one embodiment, an LED assembly is included on or within the distal
head portion of the device body. The LED assembly includes one or
more LED dies and a thermally conductive LED assembly substrate,
and the one or more LED dies are electrically coupled to one or
more contacts on the LED assembly. The one or more LED dies are
configured to emit a spectrum of light capable of curing a light
curable composition. The emitted spectrum may include one peak
wavelength in an embodiment where all LEDs are configured to emit
at the same wavelength. Alternatively, the spectrum may include two
or more different peak wavelengths where at least one of the LED
dies is configured to emit a different peak wavelength relative to
at least one other LED die.
Heat dissipation from the LED assembly may be achieved using a
thermally conductive layer on the distal head portion of the device
body between the LED assembly and the thermally conductive body
material of the device body. The thermally conductive layer is thin
and therefore lacks sufficient mass to serve as a heat sink;
however, the thermally conductive layer has a sufficiently high
surface area and thermal conductivity to serve as a conduit to
dissipate heat from the LED assembly substrate into the body
material of the device body. The material of the device body serves
as a highly efficient heat dissipater, thereby obviating the need
for a separate internal heat sink. In one embodiment,
advantageously, the dental curing device does not include an
internal heat sink. The surface area coupling the thermally
conductive layer to the device body is sufficiently large that a
majority (e.g., substantially all) of the heat conducted away from
the LED assembly by the thermally conductive layer is transferred
to the device body.
In one embodiment, the thermally conductive layer may comprise a
separate piece that is secured to a portion of the device body and
may have a thickness in a range from about 100 microns to about 1.5
mm and can be made from one or more highly thermally conductive
materials, such as, but not limited to, beryllium oxide, diamond,
aluminum nitride, or combinations of these. In another embodiment,
the thermally conductive layer may comprise a very thin layer
applied over at least a portion of the device body (e.g., by
chemical or plasma vapor deposition or plasma flame spraying). In
such embodiments, the thickness may be only about 0.05 micron to
about 50 microns. The thickness and surface area of the thermally
conductive layer is sufficient to ensure that most, if not
essentially all, of the waste heat generated by the LED is
transferred through the thermally conductive layer and dissipated
into the body material. At moderate to low operating temperatures,
the thermally conductive layer can dissipate heat from the
substrate of the LED assembly at the same rate that heat is
dissipated into the LED assembly substrate from the LED assembly,
thereby allowing continuous moderate to low temperature operation.
The use of a thermally conductive layer in contact with sufficient
surface area of the device body has been found to provide
surprisingly good heat dissipation from the one or more LEDs. The
present inventive configurations essentially eliminate the long
existing problems associated with over heating in LED-based curing
lights.
According to an alternative embodiment, individual LED
semiconductor dies may be directly mounted to the device body. In
other words, the device body becomes the substrate on which the LED
semiconductor dies are directly mounted. Power connections to the
individual dies may be made by electrically conductive metal traces
(e.g., gold) disposed on or through the thermally conductive,
electrically insulative layer formed over the device body. This is
different from the above described embodiment in which a relatively
larger LED assembly including its own LED assembly substrate is
mounted on the distal head portion of the device body. In the
alternative embodiment, the thin thermally conductive, electrically
insulative layer disposed over at least the distal head portion of
the device body is significantly thinner (e.g., about 0.05 to about
50 microns) as compared to the thickness of an LED assembly
substrate (e.g., on the order of about 500-1000 microns). Such LED
substrates must be sufficiently thick so as to provide a degree of
protection and strength to the overall LED package including one or
more LED dies mounted on the substrate. The thermally
conductive/electrically insulative layer is sufficiently thick so
as to electrically insulate the dies from the underlying body,
which may comprise metal. At the same time, the layer is relatively
thin (e.g., no more than about 50 microns, preferably no more than
about 10 microns) so as to minimize resistance to thermal
conduction through this layer. Such an embodiment may exhibit even
further improved heat dissipation as the relatively thick substrate
layer of the LED package assembly is eliminated.
In one embodiment, the curing light device includes an electronics
assembly that controls power to the one or more LED dies. The
electronics assembly can be configured to drive the one or more LED
dies at very high light intensities for extended periods of time
without overheating the LED die due to the ability to efficiently
dissipate heat away from the LED. In one embodiment, the one or
more LED dies can produce a stable emission of light of at least
about 2000 mW/cm.sup.2, at least 3000 mW/cm.sup.2, or even greater
than 3500 mW/cm.sup.2. The LED curing devices of the present
invention can achieve stable light output with one or more LEDs
that is as intense as, or even more intense than, light generated
by an arc lamp, which typically operates at 3500 mW/cm.sup.2.
Curing lights of the present invention dissipate heat through the
body, allowing the device to be operated at high power and longer
time periods compared to conventional light curing devices.
In one embodiment of the invention, the electronics assembly is
configured to minimize wavelength shifting of the output of the one
or more LED dies, even at high intensity light output. In this
embodiment, the electronics assembly is configured to power the LED
dies at a maximum power input that is substantially below the
actual maximum or rated power input of the LED die. For example,
the curing light can include an LED assembly that is rated at 10
watts, and the electronics assembly can be configured to power the
device at a maximum input power of 2.5 watts. In one embodiment,
the electronics assembly is configured to power the one or more LED
dies at a maximum power of less than about 80% of the rated maximum
input of the one or more LED dies, more preferably less than about
50%, and most preferably less than about 40% of the rated maximum
input of the one or more LED dies, while achieving a total light
output of at least about 1000 mW/cm.sup.2 from the light curing
device, more preferably at least about 2000 mW/cm.sup.2, even more
preferably at least about 3000 mW/cm.sup.2, or even at least about
3500 mW/cm.sup.2 of total light output from the light curing
device. In this way, the stability of the light output is
maintained. For example, any wavelength shift is minimized so as to
preferably be less than about 1%, more preferably less than about
0.5%, and most preferably less than about 0.1%.
In one embodiment, the underpowered device can achieve a very high
efficiency of total light output per watt of input power. In one
embodiment, the efficiency of the LED dies of the curing light can
be at least about 40%, at least about 60%, or even at least about
80% efficient. The highest efficiencies of the dental curing light
device may be achieved with configurations including a reflective
collar between the LED and the lens and/or include an
anti-reflective coating on the lens. Some embodiments may employ a
light collimating photonic crystal instead of a lens.
The device body has substantial heat dissipating capacity due to
its much larger size relative to the LED die(s) and/or LED
assembly. Because the device body serves as a heat dissipater, no
separate heat sink is required within the body of the device.
Eliminating the heat sink (as compared to typical prior art
devices) can simplify the manufacturing process and allow for
smaller, thinner, neck and distal head configurations that are more
maneuverable within the patient's mouth while providing excellent
heat dissipation. Providing a device body with a unibody
construction helps maximize heat dissipation. It also minimizes
joints and seams where debris might collect.
In one embodiment, the head portion of the device body can have a
removable cup-like member that houses the LED assembly and at least
a portion of the thermally conductive layer. The thermally
conductive layer is coupled to the LED assembly to facilitate heat
transfer from the LED(s) of the assembly to the removable member
and into the device body. The removable member can screw in or
otherwise connect to a part of the distal head portion. When
attached, the removable member becomes thermally integrated with
the distal head portion, for example, by ensuring high surface area
contact between a corresponding part of the distal head portion and
the removable member such that efficient thermal conduction through
the removable member and to the rest of the device body is
maintained.
In one embodiment, the entirety of the device body including the
handle portion, the neck portion, and the distal head portion, is
formed of a single piece of thermally conductive material.
Exemplary metals that may be used include, but are not limited to,
aluminum, copper, magnesium and/or alloys thereof. Exemplary
thermally conductive ceramic materials that may be used include,
but are not limited to, fibers or nanomaterials of carbon (e.g.,
graphene), boron, boron nitride, and/or combinations thereof.
Because the single piece body is only one piece, there are no seams
or joints within the body itself, and other interfaces within the
overall device are minimized. For example, the single piece body
(i.e., unibody construction) may include an LED head assembly hole,
a control assembly hole, and a power cord hole. The LED head
assembly hole is configured to receive the removable member
including the LED assembly. In an embodiment in which individual
LED semiconductor dies (absent any supporting LED assembly
substrate) are directly mounted onto the head of the device body,
the LED head assembly hole may be omitted. Of course, in another
embodiment individual LED semiconductor dies may be directly
mounted onto the removable member, which is later coupled into the
LED head assembly hole of the device. The control assembly hole
formed within the handle portion of the body is configured to
receive the electronics control assembly. The power cord hole
formed at the proximal end of the body is configured to receive a
power cord that is coupled to the electronics control assembly. Of
course, the body may include other holes through the body to
accommodate one or more screws or other attachment means to hold
internal components in place.
Because the entirety of the body is formed as a single piece in the
unibody construction, heat dissipation throughout the body is
improved, as seams within the body itself (i.e., where a first
piece of the body abuts a second piece of the body) can create
resistance to thermal conduction. The body advantageously has no
such abutment seams. The absence of such seams within the body also
provides for a robust dental curing light that can better withstand
rough handling and/or dropping.
These and other benefits, advantages and features of the present
invention will become more full apparent from the following
description and appended claims, or may be learned by the practice
of the invention as set forth hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the manner in which the above recited and other
benefits, advantages and features of the invention are obtained, a
more particular description of the invention briefly described
above will be rendered by reference to specific embodiments thereof
which are illustrated in the appended drawings. Understanding that
these drawings depict only typical embodiments of the invention and
are not therefore to be considered limiting of its scope, the
invention will be described and explained with additional
specificity and detail through the use of the accompanying drawings
in which:
FIG. 1 is a top perspective view of a dental curing light including
a device body having a proximal gripping end and a distal head
end;
FIG. 2 is a bottom perspective view of the dental curing light of
FIG. 1;
FIG. 3 is a cross-sectional view of the dental curing light of FIG.
1;
FIG. 4 is a top perspective view of the device body of the dental
curing light of FIG. 1;
FIG. 5 is a bottom perspective view of the device body of the
dental curing light of FIG. 1;
FIG. 5A is a cross-sectional view of the device body of FIG. 4;
FIG. 5B is a cross-sectional view of the distal head end portion of
an alternative dental curing light;
FIG. 5C is a cross-sectional view of the distal head portion of
another alternative dental curing light having an alternative
configuration;
FIG. 5D is a perspective view of the distal head end of the device
body of FIG. 5B prior to attachment of the LED dies and associated
structures;
FIG. 5E is a perspective view of the distal head end portion of
FIG. 5D once a thin electrically insulative thermally conductive
layer has been applied;
FIG. 5F is a cross-sectional view of the distal head end portion of
FIG. 5E;
FIG. 5G is a perspective view of the distal head end portion of
FIG. 5E once the LED dies have been directly mounted to the
body;
FIG. 5H is a cross-sectional view of the distal head end portion of
FIG. 5G;
FIG. 5I is a cross-sectional view of the distal head end portion of
FIG. 5H once a reflective well has been built up around the LED
dies;
FIG. 5J is a cross-sectional view of the distal head end portion of
FIG. 5I once a protective layer has been applied over the LED
dies;
FIG. 6 is a cross-sectional view of a portion of the neck of the
device body of FIG. 1 showing a scratch coating and a fluoropolymer
coating covering the surface thereof;
FIG. 7 is a cross-sectional view of the neck and head portion of
the curing light of FIG. 1;
FIG. 8 is a perspective view of an LED assembly of the curing light
of FIG. 1;
FIG. 9 is a cross-sectional view of the LED assembly of FIG. 8;
FIG. 10 is a cross-sectional view of an alternative LED assembly
including a plurality of LED dies;
FIG. 11 is a partial exploded view of the neck and head portion of
an alternative embodiment showing a removable member housing an LED
assembly;
FIG. 12 illustrates the head and neck portion of FIG. 11 with the
removable member coupled into the well of the distal head portion;
and
FIG. 13 illustrates a cross sectional view of the distal head
portion and neck portion of the device of FIG. 12.
DETAILED DESCRIPTION
I. Introduction
The present invention is directed to a dental curing light that
efficiently dissipates heat away from the light emitting diode
(LED) portion of the curing light. The device body is formed from a
thermally conductive body material, (e.g., thermally conductive
metal, polymer, ceramic, and/or thermally conductive ceramic fibers
or nanomaterials). Excellent heat dissipation away from the one or
more LEDs is achieved using a thermally conductive layer coupled to
the device body. The thermally conductive layer is disposed over at
least part of the distal head portion of the device body so as to
efficiently conduct heat away from the one or more LEDs and into
the device body. The thermal conductivity of the layer is
sufficiently high that the thermally conductive layer serves as a
conduit to quickly conduct heat away from the substrate of the LED
assembly or from direct mounted LED dies to the material of the
device body, where the heat is dissipated. In this manner, the body
material of the device body can serve as a highly efficient heat
dissipater. The surface area of the thermally conductive layer
thermally coupling the LED assembly or direct mounted LED dies to
the device body is sufficiently large that a majority (e.g.,
substantially all) of waste heat conducted into the thermally
conductive layer is quickly transferred to the device body for
dissipation. In general, the surface area of the thermally
conductive layer is advantageously larger than the surface area of
the substrate of the LED assembly or direct mounted LED dies.
For purposes of this invention, the term "majority" means greater
than 50%.
For purposes of the invention, the term "highest power setting of
the light curing device" is the highest power setting that the
device user can select, not the theoretical maximum power that
could be input into the device's one or more LEDs.
Unless otherwise stated, "rated maximum power" shall refer to the
greater of the maximum power rating provided by the LED
manufacturer having tested and rated the LED or the maximum power
input as defined by an industry standard for testing and rating
maximum power of LEDs.
II. Exemplary Dental Curing Lights
FIGS. 1-3 illustrate an exemplary dental curing light 100 including
a device body 102 having a distal head end 104 and a proximal
gripping end 106. Distal end 104 includes a neck portion 108 and a
head portion 110. Distal end 104 is sized and configured to be
inserted into the mouth of a dental patient.
The dental curing light 100 also includes an electronics assembly
112 positioned within a cavity of device body 102. The electronics
assembly 112 allows the dental practitioner to power on and off the
dental curing light 100 and control the intensity and duration of
light output from the curing light 100. The electronics assembly
can include hardware, circuitry and/or programming that allow the
LED dies to be selectively powered and operated by a user. In one
embodiment, the circuitry is programmable. Examples of programmable
circuitry is described in Applicants co-pending U.S. Patent
Application Ser. No. 61/174,562 entitled, "Dental Curing Light
Including Active And Activatable Programs For Alternate Uses,"
which is hereby incorporated by reference.
Curing light 100 includes a power cord 114 having a plug 116 that
allows the device to be coupled to a power source. However, in an
alternative embodiment, the dental curing light can have a
rechargeable battery that powers the electronics assembly. Device
body 102 may include a protective sleeve 118 attached to the
proximal end. Protective sleeve 118 may enclose the opening in the
device body 102 through which cord 114 passes and may also support
cord 114 to prevent cord 114 from developing a short.
FIG. 2 shows a bottom perspective view of dental curing light 100.
Head portion 110 includes an LED assembly 120. LED assembly 120 is
configured to emit light at one or more wavelengths suitable for
curing a dental curing composition in the mouth of a dental
patient. Holes 122a and 122b allow the electronics assembly 112 to
be secured to device body 102 using, for example, a pair of
screws.
FIG. 3 shows a cross-sectional view of dental curing light 100. The
electronics assembly 112 includes a circuit board 124, power button
126, and intensity selector 128. Power button 126 allows the dental
practitioner to power the curing light 100 on and off. Intensity
selector 128 allows the dental practitioner to increase the
intensity of the light being emitted from LED assembly 120 from a
minimum power output to a maximum power output. Actuating intensity
selector 128 increases the power delivered to LED assembly 120
through circuit board 124. To decrease power intensity, the user
can power the curing light 100 off and back on again. Alternative
control and operation modes will be readily apparent to one of
skill in the art. Wires 134 connect circuit board 124 with LED
assembly 120. Power cord 114 is also connected to circuit board 124
to supply power to electronics assembly 112.
In one embodiment, power cord 114 may comprise a high strength
fiber and/or composite material. For example, power cord 114 may
comprise a material including Kevlar and/or carbon fiber. Such
materials provide a highly flexible and supple power cord with
exceptional strength characteristics. In a preferred embodiment,
the power cord 114 is secured to device body 102 using a knot 130.
Knot 130 in power cord 114 is positioned inside power cord hole 132
of device body 102. The knot 130 abuts the device body around hole
132 and prevents the cord 114 from pulling through the hole 132.
Knot 130 has been found to be highly resistant to pulling through
hole 132 and prevents breakage by distributing a pulling force
across a larger surface area. Knot 130 can optionally be bonded or
secured to device body 102 to prevent knot 130 from being pushed
further into the cavity of the device body. Surprisingly, the
combination of a high strength cord material such as Kevlar and/or
carbon fiber and an internal knot have been found to withstand pull
out forces of greater than about 50 pounds. Power cords using a
knot may even be forcefully pulled upon (e.g., as might occur if a
practitioner tripped over the cord) without causing damage to the
connection between the power cord and the circuit board.
Circuit board 124 is electrically coupled to LED assembly 120. The
electrical connection can be any connection suitable for use in a
dental application, including, but not limited to, electrically
conductive traces and/or wires. FIG. 3 illustrates wires 134
connecting circuit board 124 to LED assembly 120.
A. Device Body
FIGS. 4, 5 and 5A illustrate the device body 102 of dental curing
light 100. Device body 102 includes a handle or gripping portion
106 that is sized and configured for a dental practitioner to hold
and manipulate with the hand. Handle portion 106 is typically
rounded and substantially wider than neck portion 108, which is
configured for insertion into a mouth of a dental patient. Neck
portion 108 is typically narrow and elongate for minimizing the
space necessary to manipulate the curing light 100 in the patient's
mouth. Head portion 110 may be wider than neck portion 108 to
provide space for an LED assembly. Other configurations (e.g.,
including direct LED die mounting and/or small, flexible organic
LED dies) may have a head portion that is as narrow as, or even
more narrow than the neck portion. In one embodiment, the device
body may be elongate. While the devices described herein typically
include structural features which configure the device for use in
the mouth of a patient, the device is not limited to use in the
mouth. Head 110 is illustrated with a recess or cavity 144 housing
the LED assembly. However, in an alternative embodiment, the head
110 can have a flat surface that supports the LED assembly (e.g.,
see FIGS. 5B-5C). As described more fully below, head 110 may also
include a removable member that includes the LED assembly.
Device body 102 includes an internal cavity 136. Cavity 136 is
sized and configured to house the electronics assembly used to
operate the dental curing light 100, including powering LED
assembly 120. Cavity 136 can include mounting points, grooves, and
other features configured to securely receive an electronics
assembly. In one embodiment, cavity 136 includes a rim 138 that is
configured to form a tight fit with a corresponding rim of
electronics assembly 112 (FIG. 3) to ensure proper sealing of
cavity 136.
Handle portion 106 also includes an end opening 132 that provides a
passageway from cavity 136 to an exterior of device body 102.
Opening 132 provides a passageway for power cord 114 as described
above. A collar 140 provides a connection for sleeve 118 that
protects cord 114 and seals opening 132, as described above with
respect to FIG. 3.
Device body 102 may include a second passageway 142 that extends
between cavity 136 and the recess or cavity 144 in head portion
110. Passageway 142 provides access between cavity 136 and 144 to
deliver power to LED assembly 120.
Device body 102 is constructed from a thermally conductive body
material. Device body 102 may be formed of any suitable thermally
conductive body material, including, but not limited to, thermally
conductive metals, polymers, ceramics, fibers and/or nanomaterials
(e.g., nanotube and/or nanosheet materials such as graphene). In
one embodiment, examples of suitable thermally conductive metals
include, but are not limited to, aluminum, copper, magnesium and
alloys thereof. In a preferred embodiment, the device body
comprises an aluminum alloy. Aluminum alloys provide a device body
that is sufficiently sturdy for use in the dental practice where
instruments are often subjected to conditions or situations that
might damage, blemish or otherwise cause deformations. Aluminum
alloys typically include alloying metals that increase the
toughness and other properties of the material. Examples of metals
that can be alloyed with aluminum or other base metals include, but
are not limited to, zinc, magnesium, copper, titanium, zirconium,
and combinations of these. In one embodiment, the aluminum alloy is
an alloy selected from the ANSI 6000 or 7000 aluminum alloy series.
A discussion of ANSI 6000 and 7000 series aluminum and other
suitable device body materials can be found in the "Handbook of
Aluminum: Volume 2: Alloy Production and Materials Manufacturing",
Jeorge E. Totten (editor), D. Scott MacKenzie, CRC; 1.sup.st ed.
(Apr. 25, 2003); "Introduction to Aluminum Alloys and Tempers", J.
Gilbert Kaufman, ASM International, 1.sup.st ed. (Dec. 15, 2000);
and "Aluminum and Aluminum Alloys: ASM Specialty Handbook", Joseph
R. Davis; ASM International (Dec. 1, 1993), all of which are hereby
incorporated herein by reference.
In one embodiment, the aluminum alloy may be ANSI aluminum alloy
6061, 6033, 6013, 6020, 7075, 7068, and/or 7050 or any alloy having
sufficient strength and thermal conductivity characteristics. In
yet another embodiment, the device body may comprise a thermally
conductive ceramic fiber (e.g., carbon fiber, boron fiber, boron
nitride fiber, or other thermally conductive fiber). In yet another
embodiment, the device body may comprise a thermally conductive
nanomaterial (e.g., a graphene nano-sheet and/or nano-tube).
Examples of thermally conductive polymers include hydrophobic
and/or hydrophilic polymers that have a thermally conductive filler
material included therein, such as, but not limited to,
nanomaterials of carbon, beryllium oxide, boron nitride, and/or
other thermally conductive ceramics and/or thermally conductive
particulate metals. Examples of thermally conductive ceramics
include aluminum nitride, beryllium oxide, silicon carbide, and
boron nitride.
The device body can include any of the foregoing thermally
conductive body materials alone or in combination. Although perhaps
less preferred, the device body may include non-thermally
conductive materials so long as substantial portions of the device
body are thermally conductive so as to dissipate the desired amount
of heat from the one or more LEDs when powered.
The device body can be a solid material in portions thereof and/or
hollow in other portions. For example, the head and neck portions
may be solid particularly in embodiments where the LED assembly is
not removable and/or where the LED dies are directly mounted onto
the thermally conductive layer. Hollow portions of the device body
can provide locations for housing various components, such as, but
not limited to, electrical components.
In one embodiment, the device body has a unibody construction. At
least a portion of the handle 106, neck 108, and head 110 can be
formed from a single piece of body material. In a preferred
embodiment, substantially all of the handle portion, neck portion
and head portion comprise a single piece of body material. The
device body 102 serves as a heat dissipater for the one or more
LEDs. Forming the body from a single piece of thermally conductive
material maximizes heat conduction into the device body 102, where
it can quickly be dissipated throughout the body and into the
air.
Such a unitary body is shown in FIGS. 4, 5, and 5A. The entirety of
device body 102, including handle portion 106, neck portion 108,
and head portion 110, is formed of a single piece of thermally
conductive material (e.g., preferably a metal such as an aluminum
alloy). Because single piece body 102 is only one piece, there are
no seams within the body 102 itself, and other interfaces are
minimized. For example, the illustrated example includes an LED
head assembly hole 144, a control assembly hole 136, and a power
cord hole 132. The LED head assembly hole 144 is configured to
receive an LED head assembly 120 (FIG. 3). The control assembly
hole 136 formed within the handle portion 106 is configured to
receive an electronics control assembly 112. Power cord hole 132
formed at the proximal end of body 102 is configured to receive a
power cord 114 that is coupled to electronics control assembly 112
(FIG. 3).
The unibody construction shown in FIGS. 4, 5 and 5A eliminates
seams and joints through the body 102 itself, and minimizes the
presence of interfaces within the device 100 overall. Because the
entirety of the body 102 is formed as a single piece, heat
dissipation throughout the body 102 is improved, as seams or joints
within a device body (i.e., where a first piece of the body abuts a
second piece of the body) can create resistance to thermal
conduction. The absence of such seams within the body 102 also
provides for a robust dental curing light that can withstand rough
handling and/or dropping. It also reduces joints or crevices where
debris or bacteria might collect.
Although LED head assembly 120 comprises a separate piece in the
illustrated embodiment (e.g., so as to provide advantages of quick
replacement if an LED or other LED assembly component fails), there
is only a single additional seam over which heat must be conducted,
as heat is conducted from the LED head assembly 120 into unitary
body 102. The presence of the single seam is a significant
improvement over configurations in which the body comprises
multiple pieces abutted and joined together. Such an embodiment
easily allows removal and replacement of the LED head assembly
(e.g., in the case of a failed LED or in order to upgrade the LED
head assembly with a different one). In an alternative embodiment,
even the LED head assembly may be integrated into the single piece
body such that there is no seam over which heat must be conducted
from the one or more LED dies into the remainder of the unitary
body. Such a configuration is shown and described in conjunction
with FIG. 5B.
Typically, the LED head assembly 120 comprises the same material as
the body 102. In preferred embodiments, these structures are formed
of metal (e.g., an aluminum alloy), and act as the only heat sink
into which waste heat generated by the one or more LED dies is
dissipated. Preferably, the LED head assembly 120 is relatively
small in mass as compared to the mass of body 102 in embodiments in
which they are separate pieces. For example, the LED head assembly
120 has a mass no more than about 25% of the mass of body 102, more
preferably no more than about 10% of the mass of body 102, and most
preferably no more than about 5% of the mass of body 102. As such,
the mass and heat dissipating characteristics of the LED head
assembly 120 are minor or insignificant as compared to body 102.
LED head assembly 120 has a relatively small mass and simply acts
to quickly facilitate conduction of heat across assembly 120 to
body 102, where it can be dissipated. As a practical matter, body
102 acts as the only heat sink.
Device body 102 preferably comprises a metal such as aluminum,
copper, magnesium, or alloys including such metals. Particularly
preferred aluminum alloys include ANSI aluminum alloys 6061, 6033,
6013, 6020, 7075, 7068, and/or 7050. 7075 is an exemplary aluminum
alloy that may be used in the manufacture of body 102. A single
piece of aluminum alloy material may be machined, cast or molded,
resulting in a unitary single piece body (i.e., unibody
construction). Machining is preferred, as it provides a body with
very narrow tolerance dimensions. Machined alloys often also
exhibit greater density and strength as compared to metals or
alloys formed by alternative methods (e.g., casting or metal
injection molding).
FIG. 5B illustrates an alternative embodiment 100' that does not
include a separate LED head assembly, but in which LED dies 160'
are directly mounted onto the distal head end 110' of the one piece
body itself. As a result, the single piece thermally conductive
body 102' does not include an LED assembly hole configured to
receive an LED assembly, as the LED die(s) are directly mounted
onto the body 102'. The head and neck portions of the device 100'
may be solid, while the proximal handle portion may include a
cavity for housing electronic control components. Although such a
configuration does not as easily allow replacement of one or more
dead LED dies or the easy replacement/upgrade of an LED assembly,
it does offer the advantage of no seam over which heat must be
conducted away from the LED dies into the single piece body. In
addition, there are advantageously no intermediate substrate layers
in between the LED die 160' and the underlying mounting layer 154'.
The elimination of such layers (e.g., primary heat sinks and/or
relatively thick substrates) further increases the heat dissipation
ability of the device as there are fewer interfaces through which
heat must be conducted. The reduction in the presence of such
interfaces may further reduce the need for relatively inefficient
thermal greases and/or epoxies typically used at the interface
between such layers.
Such a configuration is also extremely robust and resistant to
damage, as it eliminates relatively bulky LED assembly 120, which
includes thick assembly substrate 162 and package 164 (FIG. 8).
Advantageously, there are no substrate layers between the
semiconductor die 160' and the thin thermally
conductive/electrically insulative layer 154' over the thermally
conductive body. Because each LED die 160' is directly mounted to
the thermally conductive/electrically insulative layer 154' of the
thermally conductive body 102', resistance to thermal conduction of
waste heat generated from each die to the thermally conductive body
102' is advantageously minimized.
As seen in FIG. 5B, at least the distal head end 110' of unitary
body 102' includes a thin, electrically insulative and thermally
conductive layer 154' (e.g., an oxide or nitride of the underlying
metal body substrate) formed directly over the unitary body 102'.
The LED dies 160' (without any assembly substrate) are mounted on
layer 154' so as to electrically isolate them from the underlying
(e.g., metal) substrate. This thin layer 154' has a thickness
between about 0.05 micron and about 50 microns, which is sufficient
to electrically isolate the LED dies 160' from the underlying
unitary body substrate 102'. In some embodiments, it is
advantageous for layer 154' to be no thicker than required for
electrical insulation because the thermal conductivity of this
layer may be significantly less than that of the underlying metal
body 102'. For example, the thermal conductivity of aluminum alloy
7075 (e.g., the body 102') is about 130 W/m-K, while that of
aluminum oxide (e.g., layer 154') is only about 40 W/m-K. Such
issues may be less important depending on the material of layer
154'. For example, aluminum nitride has a thermal conductivity of
about 285 W/m-K. The thickness of layer 154' is greatly exaggerated
in the Figure for clarity purposes.
Although electrically insulative/thermally conductive layer 154'
may have a thickness as low as about 0.05 micron or as thick as
about 50 microns, more preferably the thickness of layer 154' is
between about 0.1 micron and about 10 microns, and most preferably
between about 0.2 micron and about 1 micron.
Layer 154' is also beneficial in minimizing effects of the
differences in thermal expansion of the underlying metal or other
conductive material body relative to that of the LED dies 160'. In
other words, there is often a significant difference between the
relatively low coefficient of thermal expansion of the LED die
relative to the high coefficient of thermal expansion of a metal
body material. The material of layer 154' may be selected so as to
exhibit a coefficient of thermal expansion that is between that of
the body material (e.g., a metal) and that of the one or more LED
dies, helping to minimize any tendency of the underlying body to
form micro-cracks and fissures after prolonged temperature cycling
during use. In some embodiments, the thermally conductive layer
(e.g., 154' or 154) may even be omitted. For example, where the
body (e.g., 102') is formed of an electrically insulative material
(e.g., carbon fiber, boron nitride, and/or graphene) the thermally
conductive layer may be omitted as a result of the excellent
thermal conductivity provided by the underlying body material
(e.g., body 102'), and the LED dies (e.g., 160') may be directly
mounted onto the electrically insulative, thermally conductive body
material (e.g., body 102'). Mounting may be accomplished chemically
(e.g., by use of a thermally conductive epoxy) and/or by mechanical
compression (e.g., using a thermally conductive grease and/or
gel).
According to one embodiment, layer 154' may be applied over the
entire unitary metal body substrate 102' or a substantial portion
thereof. Layer 154' may be applied by chemical or plasma vapor
deposition, plasma flame spraying, or other techniques that will be
apparent to those skilled in the art. Power connections to the LED
semiconductor dies 160' may be made through gold or other
conductive metal traces 170' laid down (e.g., by a deposition
process) over the layer 154', electrically insulating the traces
170' from the underlying body 102'. In order to protect traces 170'
from damage, the traces may be sandwiched between layer 154'. For
example, the layer 154' may actually be laid down as two layers
with a total thickness as described above, with the conductive
metal traces 170' sandwiched in between. Such a configuration is
shown in FIG. 5B. As illustrated, traces 170' may include one or
more power connection points 171' where trace 170' is exposed so as
to electrically contact LED dies 160'. In the illustrated
embodiment, the neck and distal head end may be solid rather than
hollow (a hollow example is shown in FIG. 7), as power connections
are made by traces 170' rather than wires fed through a hollow
head. Providing a solid neck and head may further increase heat
dissipation ability of the unitary body, as a significant fraction
of the body's mass is available directly adjacent to the heat
generating LED dies 160'. Only a single power connection point 171'
is shown for each LED semiconductor die 160' for purposes of
clarity, although another connection point (or even more than two)
may be provided in a different or even the same cross-sectional
plane.
Any of the described embodiments may further include a photonic
crystal for collimating light. Referring to FIG. 5B, dental curing
light 100' is illustrated as further including a photonic crystal
150', which acts as a light collimator. Photonic crystals are
periodic optical nano-structures that affect the motion of photons
in a similar way as semiconductor crystals affect the motion of
electrons. By way of example, some naturally occurring materials,
such as opal, peacock feathers, butterfly wings, and iridescent
beetles include photonic materials. A photonic crystal operates on
a quantum level to capture incoming photons and refract them in a
particular way. Photonic crystals are customized to specific
wavelengths or ranges that they capture and collimate. Because of
this, the crystal would be selected to capture and collimate light
of the desired wavelengths (e.g., anywhere between about 350 nm and
about 490 nm--the crystal is matched to the LED die).
As compared to a traditional lens, photonic crystals are more
efficient at collimating light. In addition, it requires less space
so as to provide better focusing/collimating ability in the small
available space. Such a crystal may be, for example, about 0.5 mm
to about 1 mm thick, which is much less than traditional lenses
that act by physically refracting light waves. Light collimating
photonic crystals may include photonic structures etched in very
thin vapor deposited films. The use of photonic crystals further
minimizes the thickness of the distal head end of the device.
Although not required, the use of photonic crystals and
implementation of direct mounting of LED dies to body 102' (or the
body of any of the other described embodiments) rather than using
an LED package assembly together works to further minimize the
overall structure of the device, for example, allowing for a very
thin distal head end that is more maneuverable within the patient's
mouth.
The LED dies themselves used with any of the described embodiments
may comprise any suitable LEDs configured to emit within the
desired spectrum. Exemplary LED dies include inorganic solid-state
LED dies and organic LED dies. Organic LED (OLED) dies are light
emitting diodes whose emissive electroluminescent layer includes a
film of organic compounds. The layer may typically include a
polymer that allows suitable organic compounds to be deposited. The
organic compounds are deposited in rows and columns onto a flat
carrier. The use of OLED dies may further reduce the thickness of
the distal head portion of the dental curing light, as OLED dies
are flexible and thinner than conventional inorganic solid-state
LED dies (e.g., the use of OLED dies alone may reduce thickness by
1-2 mm).
For example, the distal head end of any of the disclosed
embodiments may have a thickness less than about 8 mm. More
particularly embodiments including direct LED mounted dies, OLEDs,
and/or a photonic crystal for light collimation rather than a lens
may also have a thickness less than about 8 mm, more preferably
less than about 5 mm, even more preferably less than about 2 mm
(e.g., as thin as about 1 mm or less).
FIG. 5C shows a cross-sectional view of a dental curing light that
may otherwise be similar to that of FIG. 5B, but in which the neck
108'' and head portions 110'' are differently shaped, maximizing
benefits associated with the thinness of the distal head portion
110''. For example, a top surface of the body along the transition
from the neck 108'' to distal head portion 110'' is substantially
straight and flat, while the underside of the body includes a
curvature to transition from the neck portion 108'' to the thinnest
portion of the device, the distal head 110''. The proximal
grippable handle portion (not shown) may be shaped and sized
similarly to the embodiment shown in FIG. 1, as the handle portion
is the widest portion of the device, configured for gripping.
Providing a flat top surface throughout neck portion 108'' and head
portion 110'' may maximize maneuverability within the mouth,
although alternative configurations may include a flat bottom
surface or be curved on both top and bottom surfaces. Head
thickness T may be less than about 8 mm, more preferably less than
about 5 mm, more preferably less than about 2 mm, or even less than
about 1 mm. Of course, use of the above described photonic crystal
light collimators, direct mounting of LED dies, as well as the use
of OLED dies is not limited to the embodiment described in
conjunction with FIGS. 5B-5J, but such features may be used with
any of the dental curing lights described herein.
In embodiments where at least one LED die is configured to emit a
first peak wavelength (e.g., UV at about 390-410 nm) and another
LED die is configured to emit a different peak wavelength (e.g.,
blue at about 440-480 nm), more than one photonic crystal may be
required, as each crystal is customized for a particular peak
wavelength. Exemplary photonic crystals may be available from
ePIXnet, located in St. Andrews, United Kingdom; Luminus Devices,
Inc., located in Billerica, Mass.; Obducat AB, located in Malmo,
Sweden, and Daylight Solutions, Inc., located in Poway, Calif.
As illustrated, the device 100' may further include a reflective
well 168' within which the LED dies 160' are disposed. Reflective
well 168' may further aid in redirection of any emitted light
(e.g., not captured by photonic crystal 150' or in embodiments not
including crystal 150') in a desired direction. A transparent
protective layer 161' (e.g., silicone) may be applied over
structures 160' and 150' so as to protect them from being damaged
by rough handling or dropping during use. Any features described in
conjunction with the embodiments of FIGS. 5B-5J could be adapted
for use with any of the other embodiments described herein. For
example, one embodiment may include direct mounted LED dies on a
separate LED head assembly that is receivable into an LED head
assembly hole of the unitary body.
According to one method of manufacture, a unitary single piece
metallic body 102' is provided, as shown in FIG. 5D. As shown in
FIGS. 5E-5F, a thin electrically insulative and thermally
conductive layer 154' is formed over at least the distal head end
exterior surface of the metal body 102'. The thin layer 154'
preferably comprises an oxide or nitride of the underlying metal
body material 102' (e.g., in embodiments where body 102' is
metallic). It may be applied by chemical or plasma vapor
deposition, plasma flame spraying, or other techniques that will be
apparent to those skilled in the art. Conductive traces 170' may be
applied so as to be sandwiched between the electrically
insulative/thermally conductive layer 154'.
As shown in FIGS. 5G-5H, one or more LED dies 160' are then laid
down and bonded directly to an exterior surface of the thin
electrically insulative/thermally conductive layer 154', for
example, with a thermally conductive epoxy. The thickness of any
such epoxy layer is minimized so as to be extremely thin so that
its effect on resistance to thermal conductivity is negligible, as
thermally conductive thermal epoxies, although characterized as
thermally conductive, are still relatively poor thermal conductors
(e.g., perhaps as little as 1 W/m-K). Minimization of the thickness
of any such layer minimizes its negative effect on heat
dissipation. Photonic crystals 150' may be attached over LED dies
160' so as to receive emitted light.
As shown in FIG. 5I, a reflective well 168' may be attached to the
distal head end 110' of body 102' such that dies 160' are enclosed
within reflective well 168'. Although it may be possible to install
reflective well 168' prior to mounting dies 160', it is preferred
to mount dies 160' on a completely flat, smooth surface to ensure
good contact with the power connections 171' and underlying
thermally conductive/electrically insulative layer 154'.
Accordingly, reflective well 168' is preferably attached at a later
stage. Finally, as shown in FIG. 5J, a silicone or other hardenable
or curable resin protective coating may be applied over dies 160'
and photonic crystals 150' so as to protect these delicate
structures from damage. Additional details of embodiments including
direct mounted LED dies may be found in U.S. Patent Application
Ser. No. 61/141,482 filed Dec. 30, 2008, previously incorporated by
reference.
The dental curing device can have any shape suitable for use as a
curing device. In one embodiment, the dental curing device can have
an elongate shaped body to facilitate use of the device in the
mouth of a patient. An elongate shape of the dental curing device
is but one example of a dental curing light within the scope of the
invention. It will be appreciated that the dental curing light may
have other shapes suitable for use in curing a dental composition
within, or even outside, a patient's mouth. For example, curing
lights known in the art having a gun-like configuration may
incorporate any of the features disclosed herein. In general, any
known curing light configuration may be used in connection with the
features described herein.
Because the device body serves as a heat dissipater, there is no
requirement for a cavity, opening, or other configuration of the
device body to accommodate a separate metal body thermally coupled
to the LED with sufficient heat capacity to function as a heat
sink. The ability to remove the "traditional heat sink" from the
dental curing light devices described herein allows for a low
profile dental curing light device to be manufactured. In
particular, the neck and head portions can be made much smaller
and/or thinner and/or accommodate larger LED assemblies compared to
dental curing lights that use a separate heat sink housed within
the head or neck portions of the curing light devices. An
embodiment including an extremely thin distal head is shown in FIG.
5C.
Because device body 102 comprises a thermally conductive material,
it can serve as a heat conductor and dissipater. Furthermore, the
device body 102 can be made more solid and thinner as compared to
the housing of plastic body dental curing lights. In one
embodiment, the thermally conductive body material is of a metal
construction that provides increased strength and durability while
still achieving a smaller, more maneuverable curing light.
In one embodiment, the handle portion of the device body can have a
thickness in a range from about 10-40 mm, more preferably about
15-30 mm. Such dimensions provide for comfortable gripping by the
user. The neck and head portions are thinner than the handle
portion and can have a thickness in a range from about 1-15 mm,
more preferably about 1-10 mm. As described above, a head portion
thickness less than about 8 mm, more preferably less than about 5
mm, or even less than about 2 mm may be possible when using one or
more of direct die mounting, photonic crystal light collimation, or
organic LEDs.
B. Protective Coating
In one embodiment, all or a portion of the exterior surface of the
device body includes one or more coatings. For purposes of this
invention, the exterior surface of device body 102 is the surface
that is exposed in the assembled curing light or covered by a
coating layer that does not substantially change the shape of the
surface. For example, in the embodiment illustrated in FIGS. 1-5,
the surface of neck portion 108 is an exterior surface, but the
surface of interior cavity 136 is not an exterior surface since
electronics assembly 112 covers up the surface. Similarly collar
140 as illustrated in FIGS. 1-5 is not an exterior surface since it
is covered by protective sleeve 118. However, if desired, portions
of device body 102 that do not provide an exterior surface may be
coated.
The exterior surface of device body 102 may be coated with one or
more coatings to protect the surface and/or to facilitate cleaning
and/or sterilizing the curing light 100. In one embodiment, the
exterior surface of device body 102 may be coated with a scratch
resistant coating and/or a fluoropolymer coating. FIG. 6 is a
cutaway view of a portion of the neck portion 108 of device body
102 illustrating a protective coating. A scratch resistant coating
146 is positioned adjacent the surface of device body 102. The
coating layers may be applied by chemical or plasma vapor
deposition, plasma flame spraying, or other techniques that will be
apparent to those skilled in the art.
Scratch resistant coating 146 can be a thin layer of any material
that has a hardness greater than the body material of device body
102. In one embodiment, the scratch resistant layer can be a metal
oxide or a metal nitride. The scratch resistant layer may be the
same as the thermally conductive layer. In one embodiment, the
scratch resistant coating 146 can be an anodized layer formed on
the surface of a metallic device body 102. For example, where the
metallic body material includes aluminum, anodizing the surface of
the device body 102 creates an aluminum oxide surface. In a
preferred embodiment, the scratch resistant coating 146 is between
about 0.05 micron to about 100 microns thick (not shown to scale in
FIG. 6). Preferably the thickness is greater than about 1 micron,
more preferably greater than about 10 microns, and most preferably
greater than about 25 microns. In one embodiment, the thickness can
be in a range from about 1 micron to about 40 microns or,
alternatively, in a range from about 5 microns to about 50
microns.
While the thickness of the scratch resistant layer can depend
somewhat on the material being used and the desired scratch
resistance, for anodized aluminum, the thickness of the scratch
resistant layer must be substantially greater than about 5-15 nm,
which is the thickness of self-passivated aluminum, which is known
to not have a thickness sufficient for imparting scratch
resistance.
In a preferred embodiment, the hardness of the scratch resistant
coating is greater than about 55, more preferably greater than
about 60, and most preferably greater than about 65 on the Rockwell
C scale. The hardness is typically in a range from about 60-90,
more preferably about 65-80 on the Rockwell C scale. Examples of
suitable scratch resistant coatings include aluminum oxide,
aluminum nitride, chrome nitride, chrome oxide, zirconium oxide,
titanium nitride, tungsten carbide, silicon carbide, chrome
carbide, and combinations thereof.
The fluoropolymer coating 148 that may be applied to an exterior
surface of the device body can provide a surface that minimizes
friction so as to render device highly maneuverable within the
mouth. Furthermore, the device is easily sterilized and less prone
to retain bacteria and/or debris, which is important since the
dental curing light is used in the mouth of a dental patient and
must be cleaned between uses to avoid contamination and infection
between dental patients. In one embodiment, the fluoropolymer
coating has a thickness in a range from about 0.05 micron to about
10 microns, more preferably about 0.1 micron to about 1 micron.
Examples of suitable fluoropolymers include, but are not limited
to, polytetrafluoroethylene, perfluoroalkoxy polymer, fluorinated
ethylene-propylene, polyethylenetetrafluoroethylene,
polyethylenechlorotrifluoroethylene, polyvinylidene fluoride,
polychlorotrifluoroethylene, and combinations of these. Although
perhaps not technically a fluoropolymer, a parylene coating (e.g.,
applied by chemical vapor deposition) may additionally or
alternatively be applied. Parylene is a polymer manufactured from
di-p-xylylene. It can be applied in a thin, clear layer, and is
biocompatible. As used herein, "fluoropolymer coating" is to be
broadly construed to also include parylene coatings. Parylene
coatings may include Parylene N, Parylene C, Parylene D, Parylene
AF-4, Parylene SF, Parylene HT, Parylene A, Parylene AM, Parylene
VT-4, Parylene CF, and Parylene X.
The fluoropolymer coating 148 may be used alone or in combination
with the scratch resistant coating 146. However, the use of a
scratch resistant coating 146 under fluoropolymer coating 148 has
been found to provide substantial benefits that cannot be achieved
by either layer alone. For example, fluoropolymer coating 148 can
be difficult to bond to some metallic surfaces. In one embodiment,
the scratch resistant coating 146 is selected to provide good
adhesion of the fluoropolymer coating 148 to the exterior surface
of device body 102. For example, metal oxides such as aluminum
oxide provide good bonding between aluminum alloys and
fluoropolymers such as polytetrafluoroethylene.
The scratch resistant coating 146 can also prevent abrasion of
fluoropolymer coating 148, even in embodiments where the scratch
resistant coating is positioned below the fluoropolymer coating.
The hardness of the scratch resistant coating helps to prevent the
formation of dents within the body material, so that the exterior
surface remains smooth, and objects or materials contacting the
fluoropolymer surface will slide off the surface without
substantially abrading the surface. If a scratch, dent, or other
defect were to develop on the surface of the device body, the
fluoropolymer coating may be more easily abraded at the edge of the
defect. The inclusion of the scratch resistant coating 146 helps to
prevent this from occurring. The scratch resistant coating and/or
the fluoropolymer coating may each comprise a single layer or one
or both may include two or more sublayers.
C. Head Portion Including LED and Thermally Conductive Layer
In one embodiment, the head portion 110 of device body 102 includes
an LED assembly 120 that allows a dental practitioner to illuminate
a polymerizable composition and cause the polymerizable composition
to cure. FIG. 7 is a partial cutaway view of dental curing light
100 illustrating the distal end portion 104 in greater detail. Head
portion 110 supports or contains LED assembly 120. LED assembly 120
may include a lens 150, an LED package 152, and a thermally
conductive layer 154. In the embodiment of FIG. 7, thermally
conductive layer may comprise a separate, relatively thick member
that is secured to body 102, rather than being a very thin layer
applied by vapor deposition or plasma flame spraying techniques, as
that shown in FIGS. 5B and 5D-5J. Of course, an alternative in
which a relatively thin thermally conductive layer is applied to
body 102 (e.g., by vapor deposition or plasma flame spraying) is
possible.
LED package 152 and thermally conductive layer 154 are disposed
within cavity 144. Wires 134 and 134b extend through passageway 142
and provide power to LED package 152. LED package 152 and thermally
conductive layer 154 are secured to the floor 156 of cavity 144.
Floor 156 is typically flat to facilitate good contact between
thermally conductive layer 154 and the surface of floor 156.
However, other configurations can be used so long as the surface
area in contact between the device body 102 and the thermally
conductive layer 154 is sufficient to quickly conduct the heat
produced by the one or more LED dies through thermally conductive
layer 154 during use. Thermally conductive layer 154 can be
thermally coupled, bonded, or otherwise secured to floor 156 using
any technique that ensures good thermal contact. Thermally
conductive layer 154 is thermally coupled to LED package 152
through LED assembly substrate 162, which may be part of package
body 164, which is described more fully below with reference to
FIGS. 7-8.
The thermally conductive layer 154 includes at least a first layer
of a highly thermally conductive material. The thermal conductance
of the first layer material is preferably greater than about 150
W/m-K, more preferably greater than 170 W/m-K, even more preferably
greater than 200 W/m-K, and most preferably greater than about 300
W/m-K. In one embodiment the conductivity can be in a range from
about 150 W/m-K to about 2000 W/m-K, more preferably about 170
W/m-K to about 500 W/m-K. Examples of first layer materials that
may be used to make thermally conductive layer 154 include, but are
not limited to, aluminum nitride, beryllium oxide, diamond, silicon
carbide, boron nitride, nanomaterials of carbon (e.g., carbon
fiber, carbon nanotube fiber, and/or graphene), beryllium oxide,
boron nitride, and/or other thermally conductive ceramics and/or
thermally conductive particulate metals and/or ceramics and/or
derivatives thereof and/or combinations thereof.
In one embodiment, the first layer of the thermally conductive
layer 154 is not electrically conductive. The use of
non-electrically conductive materials in the first layer allows the
thermally conductive layer to include traces. The traces can be
patterned to electrically couple to the contacts of the LED
assembly substrate to provide power to the LED dies. The traces can
be made from any material useful for making traces, such as, but
not limited to, gold, copper, silver, platinum, or aluminum. In one
embodiment, the traces can be provided by a copper pad or
plate.
In one embodiment, the first layer of the thermally conductive
layer 154 is made of a material that has a coefficient of thermal
expansion that is substantially matched to a coefficient of thermal
expansion of the LED assembly substrate 162.
In one embodiment the thermally conductive layer can be a thermally
conductive printed circuit board. The thermally conductive printed
circuit board can be a ceramic circuit board or a metalized printed
circuit board. Those skilled in the art of circuit boards are
familiar with techniques for manufacturing thermally conductive
printed circuit boards.
In one embodiment, the thermally conductive layer can include a
deformable layer such as a thermally conductive deformable pad
and/or a thermally conductive gel or grease layer. Typically the
deformable layer is positioned below the first layer (i.e.,
adjacent the device body). Examples of thermally conductive greases
include silicon greases, polymer greases, metalized greases, and
nanoparticle greases. Nano-particle greases typically include a
thermally conductive filler (e.g., ceramic, carbon, or
diamond).
Examples of thermal gels are available from the following companies
at the following website, the content of which is hereby
incorporated herein by reference:
TABLE-US-00001 ShinEtsu: web page microsi.com/packaging/thermal_gel
at the domain htm AiT Technology: web page
aitechnology.com/products/ thermalinterface/thermgel/ Ultra +5: web
page tigerdirect.com/applications/SearchTools/
item-details.asp?EdpNo=3298395&CatId=503 Masscool Thermal Gel:
web page tigerdirect.com/applications/
searchtools/item-details.asp?EdpNo=480215&csid=_21
The thermally conductive grease, gel, or adhesive can include a
filler material to improve thermal conductivity. Examples of
thermally conductive filler materials include aluminum nitride,
beryllium oxide, carbon, diamond, silicon carbide, boron nitride,
and combinations of these and/or nanomaterials thereof. In some
embodiments, a separate thermally conductive layer 154 may not be
required. For example, depending on the characteristics of the LED
assembly and the LED assembly substrate 162 included therein, no
additional thermally conductive layer 154 may be required. In such
an example, the LED assembly substrate 162 effectively serves as a
sufficient thermally conductive layer, and may simply be coupled to
the underlying body of the dental curing light with a thermally
conductive grease, gel, or adhesive. Such LED assembly substrates
162 would preferably have surface area and thickness
characteristics similar to the characteristics described herein
relative to a separately employed thermally conductive layer
154.
In a preferred embodiment, the thermally conductive layer 154 has a
higher thermal conductivity than the thermal conductivity of the
material used in the device body (e.g., the material that forms the
surface of floor 156, for example an aluminum alloy).
The thermally conductive layer 154 is thin relative to body 102 and
therefore lacks sufficient mass and heat capacity to serve as a
heat sink. In one embodiment, the thickness of the thermally
conductive layer 154 is in a range from about 100 microns to 1.5
mm, more preferably about 200 microns to about 1 mm and most
preferably about 500 microns to 900 microns. The thickness of such
layer 154 is significantly greater than embodiments in which the
thermally conductive layer comprises a layer applied by vapor
deposition or plasma flame spraying techniques. For example, such
layers may only have a thickness between about 0.05 micron and
about 50 microns. In any case, the thermal conductivity of the
layer 154 is sufficiently high that the thermally conductive layer
154 serves as a conduit to dissipate heat from the one or more LED
dies to the material of the device body. In this manner, the
material of the device body can serve as a highly efficient heat
dissipater. The surface area coupling the thermally conductive
layer to the device body is sufficiently large that a majority of
heat being conducted by the thermally conductive layer is
transferred to the device body.
The thermally conductive layer 154 is thermally coupled to the LED
package 152 and the device body 102. The thermal coupling of the
thermally conductive layer 154 to the LED package 152 and the
device body 102, in combination with the thickness of the thermally
conductive layer, can be selected to ensure that most, if not
essentially all, the heat generated by the LED dies during use of
the curing light 100 is quickly conducted into the body material
for dissipation. Because the configuration is so efficient at
conducting heat away from the LED dies, low to moderate
temperatures are maintained, even during continuous operation.
In a preferred embodiment, layer 154 has substantially more
contactable planar surface area than package 152. Oversizing the
thermally conductive layer 154 can significantly improve heat
dissipation by transferring heat to the device body around the
periphery of LED package 152. The use of the device body as a heat
dissipater allows ample surface area in which the thermally
conductive layer can transfer heat at a significant rate from the
LED package 152. Thus, the thermally conductive layer utilizes the
heat capacity of the device body much better than directly coupling
the LED package 152 to the device body. In general, because the
thermally conductive layer 154 has a higher thermal conductivity
than the device body, the larger the surface area coupling the
thermally conductive layer 154 and the device body 102, the greater
the rate of heat transfer to the device body.
The use of a thermally conductive layer in contact with sufficient
surface area of a device body has been found to provide
surprisingly good heat dissipation from the LED package. The
configuration used in the present invention essentially obviates
the long existing problems associated with over-heating in
LED-based curing lights.
As mentioned, the thermally conductive layer 154 can have a thermal
conductivity that is greater than that of the device body. In one
embodiment, the thermally conductive layer 154 has a higher thermal
conductivity than aluminum alloys. While the device body can be
made from several different materials, aluminum alloys have been
found to provide a good balance between heat capacity/thermal
conductivity and manufacturability and durability of the device
body. Although aluminum alloys tend to have poorer heat transfer
characteristics than pure aluminum, the thermally conductive layer
provides quick dissipation to a sufficiently large area of the
aluminum alloy to overcome the disadvantages of using aluminum
alloys compared to pure aluminum. This is a surprising and
unexpected result.
As shown in FIG. 7, curing light 100 may include a focusing lens
150 used to focus the light generated by LED package 152. The
focusing lens 150 can be any lens suitable for collimating light
with the wavelengths and light intensities utilized in the dental
curing light 100. While FIG. 7 illustrates a traditional refractive
lens configuration, the present invention may include other types
of lenses, including photonic crystals for light collimation.
In one embodiment, assembly 120 includes the one or more LED dies
in a package. Any LED package suitable for use in curing
polymerizable compositions that can be coupled to a thermally
conductive layer, and thereby coupled to the device body 102, can
be used in the present invention. Moreover, two or more LED
packages having one or more additional LED dies emitting at the
same or a different wavelength can be used in the dental curing
lights of the present invention. An exemplary LED package 152 is
illustrated in FIGS. 8-9. LED package 152 includes an LED die 160
that is mounted on an assembly substrate 162 of package body 164.
Assembly substrate can be used alone or in combination with any
other features of an LED package. For example, in the non-limiting
example shown in FIGS. 7 and 8, package body 164 surrounds LED die
160 and forms a package cavity 166 having a floor 167. Package
cavity 166 typically has a slanted wall 168. Wall 168 and/or other
surfaces of package 152 can be coated with a reflective coating to
limit absorption of light generated by LED die 160 and maximize
light output. In addition, the same or a different reflective
coating can be applied to internal surfaces of head cavity 144 and
head 110 to minimize absorption of light from LED die 160. Examples
of suitable reflective materials include, but are not limited to,
noble metals, preferably rhodium. In one embodiment, package 152
can have a reflective collar and/or an antireflective coating
similar to the collar and anti-reflective coating described below
in conjunction with FIG. 13.
LED assembly substrate 162 can comprise any material suitable for
supporting LED die 160, so long as substrate 162 has a sufficiently
high thermal conductivity to transfer heat from die 160 to
thermally conductive layer 154 (FIG. 7). In one embodiment,
substrate 162 can be formed of the same or a similar material as
the first layer of thermally conductive layer 154. LED assembly
substrate can be made from one or more sublayers and can be made
from one or more different thermally conductive materials so long
as the desired thermal conductivity is maintained. LED die 160 can
be provided as a prepackaged LED package or alternatively, the LED
package can be created in-situ on the device body.
The LED dies are selected to emit at a desired wavelength for
curing a polymerizable composition. The LED die is typically
configured to emit at a particular wavelength within the range from
about 350 nm to about 490 nm, although the invention is not
necessarily limited to devices that emit at these wavelengths.
Light curable dental compositions typically include light activated
initiators that only respond to a very narrow range of wavelengths.
For example camphorquinone is activated by blue light, while many
proprietary initiators are activated by UV light. LED dies that are
selected to operate at the desired wavelength are important for
achieving curing in the desired manner and time interval for the
particular polymerizable composition. In one embodiment, the LED
package can have one or more LED dies configured to emit light at a
particular frequency in a range from about 350 nm to about 490 nm.
In a preferred embodiment, the LED package can emit light at least
in the UV spectrum and separately or simultaneously in the blue
spectrum. Examples of suitable LED packages and dies that can be
used in the dental curing lights of the present invention are
disclosed in U.S. Pat. No. 7,473,933 to Yan, which is hereby
incorporated herein by reference.
Power connections to the LED die 160 can be made through contacts
170a and 170b. In this embodiment, the contacts may be embedded in
substrate 162. However, in other embodiments, contacts may be
placed in other structures of the package body or other components
of the LED assembly. Contacts and traces to LED die 160 may be made
from gold or other conductive metal traces deposited using known
techniques such as, but not limited to, deposition techniques.
While LED package 152 has been illustrated as receiving power from
wires 134a and 134b, power can be supplied using traces or leads or
any other technique suitable for delivering power to the LED die.
In one embodiment, traces to LED package 152 can be embedded in an
electrically insulative coating such as the scratch resistant
coating or an applied thermally conductive layer as described in
conjunction with FIGS. 5B and 5D-5J. In this embodiment, the
electrical contact (e.g., wires or traces) between head 110 and
cavity 136 can travel along the outside of neck portion 108 of
device body 102. The wires or traces can be embedded in the coating
by using a first electrically insulating layer such as aluminum
oxide beneath the traces and then another electrically insulating
coating layer such as aluminum oxide above the traces. The
insulating coating layers can be aluminum oxide, aluminum nitride
or any other suitable electrically insulating coating. The lower
insulating layer can be formed by anodizing an aluminum body and
the upper insulating layer can be formed by plasma flame
spraying.
FIG. 10 illustrates an alternative embodiment of the invention
including a plurality of LED dies 260a, 260b, 260c, and 260d. The
use of multiple dies allows the package 252 to emit at more than
one wavelength and/or emit more light at one wavelength. In one
exemplary embodiment, LED dies 260a and 260b are configured to emit
light in a range from about 460 nm to about 470 nm, die 260c is
configured to emit light in a range from about 445 nm to about 455
nm, and die 260d is configured to emit light in a range from about
400 nm to about 410 nm (e.g., about 405 nm). LED package 252 can
include any number of dies so long as there is physical space
available for the die footprint. The LED dies may be configured to
emit light at any frequency suitable for curing a light
polymerizable composition. LED package 252 includes contacts
270a-270c for driving LED package. The LED dies can be driven in
series or parallel and at voltages and power outputs similar to
those discussed with respect to FIGS. 1-9.
D. Alternative Dental Curing Lights
FIGS. 11-13 illustrate an alternative dental curing light 200 that
includes a head portion having a removable cup-like member 280.
Removable member 280 houses an LED package 252 that is coupled to
removable member 280 using a thermally conductive layer 254. The
thermal conductance between LED package and device body 202 is the
same as for curing light 100 except that head 210 includes coupling
means for securing member 280 to a part of head 210.
In one embodiment, the coupling is provided by a threaded body 282
and threads 284 on member 280 allows removable member 280 to be
screwed into threaded body 282 of head 210. A floor 256 of well or
cavity 244 is in intimate contact with a bottom surface 286 of
removable member 280. The relatively large surface area of bottom
286 of removable member 280 and floor 256 of cavity 244 ensure good
heat transfer between the parts of head 210. The connection between
removable member 280 and cavity 244 can be made using any removable
connection such as, but not limited to, threads, a snap fit
connection, pin connector, or similar connection that provides a
similar functionality.
Removable member 280 can be made from the same materials as the
other parts of device body 202 as described above with respect to
device body 102. In one embodiment, removable member 280 is made
from the same material as device body 202. However, in an
alternative embodiment, removable member 280 may comprise a metal
or other thermally conductive material that has higher thermal
conductivity compared to the other parts of device body 202.
The electrical connection between wires 234 and LED package 252 may
be accomplished by providing a pair of spring loaded contacts 290a
and 290b. Removable member 280 includes corresponding electrical
contacts 292a and 292b that compress spring loaded contacts 290a
and 290b as removable member 280 is screwed down. Any electrical
coupling means can be used so long as electrical contact can be
made with removable member 280 securely seated in cavity 244.
The use of a removable member 280 allows LED package 252 to be
relatively easily replaced or upgraded. To replace or upgrade the
LED package 252 with a repaired or improved LED package, the
removable member 280 can be removed and a new removable member 280
including a new LED package 252 can be screwed into or coupled onto
head 210. Dental practitioners can thereby avoid the expense of
returning the entire device to a manufacturer (as in the case of a
broken device) or discarding the entire device when a newer device
is desired. Removable member 280 can be used in combination with
any of the features described above with regard to any of the
disclosed curing lights.
FIG. 13 also illustrates a reflective collar 294 that defines an
opening having an interior surface 295. Reflective collar 294
reflects and channels light from LED package 252 to lens 250. In a
preferred embodiment, reflective collar 294 has a cylindrical
shape; however, if desired, other shapes may be used. Reflective
collar 294 may include a reflective coating on interior surface 296
that improves the reflectivity of light on the surface thereof,
thereby reducing absorption. The reflective coating is preferably a
high sheen noble metal coating. Rhodium and palladium are examples
of suitable noble metals and rhodium is particularly preferred.
Noble metals are preferred for their ability to resist tarnishing,
which can reduce reflectivity over time.
In one embodiment, the components of removable member 280 can be
secured using a snap fit 298 created between a portion of lens
housing 300 and threaded body 282. Reflective collar 294 can be
secured within removable member 280 by wave spring 302 that abuts
first washer 304, which also abuts lens housing 300. A second
washer 306 separates reflective collar 294 from the bottom of
removable member 280. The reflective collar 294 can be secured
using a different type of spring, or with a different type of
connection mechanism, such as, but not limited to, an adhesive.
In one embodiment, lens 250 has an antireflective coating on the
surface thereof. The anti-reflective coating is preferably on the
surface facing the LED dies; however, other surfaces can also be
coated. The anti-reflective coating reduces reflection of the light
off the surface of the lens, thereby increasing the percentage of
light that passes through lens 250 and reduces absorption caused by
light reflected off lens 250. Examples of anti-reflective coatings
include, but are not limited to, magnesium fluoride. Of course, one
or more collimating photonic crystals may be used as an alternative
to lens 250.
The foregoing structures and coatings shown with respect to the
embodiment of FIG. 13 can be used in combination with the features
described in FIGS. 1-10 above.
In another alternative embodiment of the invention, the dental
curing light includes a rechargeable battery in the cavity of the
handle portion of the device body. In this embodiment, an
electrical plug or other connection at the proximal end of the
handle portion replaces the power cord and allows the dental curing
light to be connected to a charging station or base for recharging
the battery. Underpowering the LED package as described above is
particularly advantageous when used in combination with a
rechargeable battery to allow higher power output for a longer
period of time without recharging and/or to reduce the size of the
battery pack while achieving desired periods of use between
recharging.
III. Operating Configurations of Dental Curing Lights and Methods
of Use
The dental curing lights of the present invention can be configured
to emit at very high light output and/or to emit continuously at
low operating temperatures and high efficiencies. In one
embodiment, the curing light device includes an electronics
assembly that controls power to the LED package. The electronics
assembly can be configured to drive the LED die at very high light
intensities for extended periods of time without overheating the
LED die.
In one embodiment, the LED package can produce stable emission of
total light output of at least about 2000 mW/cm.sup.2, at least
3000 mW/cm.sup.2, or even greater than 3500 mW/cm.sup.2. For
purposes of the present invention, unless otherwise indicated,
total light output is measured using a thermopile measurement
device. Other types of light measuring devices that can be used in
some embodiments include spectrometers and Demetron
Radiometers.
The LED curing devices of the present invention can achieve stable
light output with an LED that is as intense as or even more intense
than light generated by an arc lamp, which typically operates at
3500 mW/cm.sup.2. The ability to emit light at such high light
outputs using an LED light source is due in part to the use of the
device body as a heat dissipater and the use of the thermally
conductive layer to quickly and efficiently conduct the head away
from the LED dies to the device body, where the heat is
dissipated.
In one embodiment of the invention, the electronics assembly is
configured to minimize wavelength shifting of the output of the LED
dies, even at high intensity output. In this embodiment, the
electronics assembly is configured to power the LED dies at a
maximum input power that is substantially below the actual maximum
or rated power of the LED dies. For example, the curing light can
include one or more LED dies that are rated for operation at about
10 watts and the electronics assembly can be configured to power
the device at a maximum input power of about 2.5 Watts.
In one embodiment, the electronics assembly is configured to power
the LED package at a maximum input power of less than 80% of the
rated maximum power of the LED dies, more preferably less than
about 50%, even more preferably less than about 40%, and most
preferably less than about 30% of rated maximum power, while
achieving a light output of at least about 500 mW/cm.sup.2, more
preferably at least about 800 mW/cm.sup.2, more preferably at least
about 1000 mW/cm.sup.2, even more preferably at least about 2000
mW/cm.sup.2, or even at least about 3000 mW/cm.sup.2.
In one embodiment, the LED curing light can be configured to have a
very high efficiency of total light output per watt of power input,
even at high light output. The devices of the invention can be
configured to have an efficiency of total light output that is
significantly greater than the typical efficiencies in high powered
curing lights previously known, which tend to have efficiencies of
total light output per watt of input power in the 10%-30% range. In
one embodiment, the efficiency of the LED dies of the curing light
of the invention is at least about 40%, more preferably at least
about 50%, even more preferably at least about 60% and most
preferably at least about 70%, where the efficiency is measured
according to the watts of total light output from the curing light
per watt of input power to the LED dies. For example in one
embodiment, a curing light having an LED package with 4 LED dies
and a rated power of 10 watts is operated at 6 watts and outputs a
total light intensity of 3500 mW/cm.sup.2. The highest efficiencies
of the dental curing light device may be achieved with
configurations including a reflective collar between the LED and
the lens or photonic crystal. The use of an anti-reflective coating
on any employed lens further improves efficiency.
Driving the LED dies at a fraction of their rated maximum power
minimizes temperature cycling of the LED dies and nearby structure.
This technique is particularly advantageous for use with LED
configurations that include two or more LED dies. Driving a first
LED die below its rated power ensures that the adjacent LED die
emits at its design wavelength at a desired power output. Thus, a
plurality of LED dies can be simultaneously operated at one or more
desired wavelengths continuously for an extended period of time
without causing detrimental wavelength shift or significant power
drop in any of the LED dies as a result of overheating.
Underdriving the LED package results in reduced operating
temperatures near the LED die. In one embodiment, the temperature
in the LED package adjacent the dies can be kept below about
80.degree. C., more preferably below about 70.degree. C., and most
preferably below about 50.degree. C., which is much cooler than the
typical maximum operating temperatures (e.g., more than 125.degree.
C.) of traditional curing light systems. The cool running curing
lights of the invention can be inserted into the mouth of the
dental patient without fear of burning the patient or causing
discomfort. Although some embodiments of the invention include
underdriven LED dies, in other embodiments it may be desirable to
overdrive the LED to produce a shift in wavelength.
In one embodiment of the invention, the power input and light
output of the dental curing light 100 can be ramped over a period
of time. The low operating temperature and/or high light output of
the curing lights of the present invention provides for many
possible ramp times and light output intensities. A ramp time may
be appropriate for one scenario but not for another. In one
embodiment, the dental curing light may include circuitry
configured to allow the user to choose a ramp time for ramping up
the light output of the dental curing device. In one embodiment, an
electronics assembly of the dental curing device includes a
plurality of selectable ramp times within a range from about 2-20
seconds, more preferably 5-15 seconds. Exemplary selectable times
include 5 seconds, 10 seconds, 15 seconds, and 20 seconds. In this
embodiment, the user selects one of the plurality of ramp times and
the device incrementally increases power input to reach the
selected light output intensity in the selected period of time. For
example, if the selected light intensity output is 2000 mW/cm.sup.2
and the user selected ramp time is 5 seconds, the electronics
assembly incrementally increases power input to the LED die to
reach a light intensity output of 2000 mW/cm.sup.2 within 5
seconds. Using the same device, the user can select a different
ramp time, such as 3 seconds, and the electronics assembly will
incrementally increase input power to the desired light intensity
output (e.g., 2000 mW/cm.sup.2) within 3 seconds. Additional
details regarding ramping are described in U.S. Patent Publication
No. 2006/0033052 to Scott, which is hereby incorporated herein by
reference.
The present invention also includes methods of curing a
polymerizable composition using a dental curing light. The method
includes (i) providing a dental curing light according to one or
more of the foregoing embodiments, (ii) depositing a light curable
composition within the oral cavity of a patient, and (iii) curing
the composition using the dental curing light by directing a beam
of light toward the polymerizable composition for a sufficient
amount of time to cure the light curable composition, the beam of
light having a light intensity of at least about 2000 mW/cm.sup.2.
The dental composition includes a polymerizable component and a
photo initiator that is sensitive to light at the wavelength
emitted from the light curing device. Examples of light curable
dental compositions are disclosed in U.S. Patent Publication No.
2006/0194172 to Loveridge, which is hereby incorporated herein by
reference. Those skilled in the art are familiar with wavelengths
and compositions for placing and curing a curable composition in
the tooth of a patient.
It will be appreciated that the present claimed invention may be
embodied in other specific forms without departing from its spirit
or essential characteristics. The described embodiments are to be
considered in all respects only as illustrative, not restrictive.
The scope of the invention is, therefore, indicated by the appended
claims rather than by the foregoing description. All changes that
come within the meaning and range of equivalency of the claims are
to be embraced within their scope.
* * * * *
References